Process for introducing fluorine atoms into aromatic rings by nucleophilic exchange

Abstract

Aromatic, ring-fluorinated compounds are particularly advantageously prepared by nucleophilic exchange in the course of reaction wih potassium fluoride in the presence of phase transfer catalysts and, if desired, solvents by carrying out the reaction in the additional presence of metal salts.

We claim: 
     
       1. In the preparation of an aromatic ring-fluorinated compound by nucleophilic exchange between an educt and potassium fluoride in the presence of a phase transfer catalyst, the improvement wherein the educt is selected from the group consisting of 3,4-dichloro-nitrobenzene, 2,4-dichloro-nitrobenzene 2,4-dichloro- 5-fluoro-benzoyl chloride, 3,4-dichloro-benzoyl chloride, 2,6-dichloro-benzonitrile, 2-nitro-6-chlorobenzonitrile, 2-trifluoromethyl-4-nitrochlorobenzene, pentachlorobenzotrifluoride, 4-trifluoromethyl-tetrachlorobenzoyl chloride and 3,4,5-trichlorobenzotrifluoride, the phase transfer catalyst is a quaternary nitrogen compound, a quaternary phosphorus compound, a pyridinium salt or a crown ether, and the reaction is effected in the additional presence of a salt of a metal of main groups 3 to 5 of the periodic table of the elements and of sub-group elements, the reaction is effected at from about 100° to 250° C., about 0.1 to 10 moles of the metal salt being present per mole of phase transfer catalyst, and about 0.1 to 20 mole % of the phase transfer catalyst being present based on the educt. 
     
     
       2. A process according to claim 1, in which dimethyl sulphoxide, N-methylpyrrolidone, tetramethylene sulphone, benzonitrile, nitrobenzene, dimethylacetamide, ethylene glycol demethyl ether or diglyme are employed as solvents. 
     
     
       3. A process according to claim 1, in which 1.1 to 2 moles of potassium fluoride are employed per mole of fluorine atoms to be introduced. 
     
     
       4. A process according to claim 1, in which all components of the reaction mixture are employed in dry form. 
     
     
       5. A process according to claim 1, in which small amounts of water present in the reaction mixture are removed by distilling off. 
     
     
       6. A process according to claim 1, in which the metal of the salt of a metal of main groups 3 to 5 of the periodic table is selected from the group consisting of chromium, iron, cobalt, nickel, copper, aluminum, zinc and antimony.